<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    @keyframes size-animation {
      from {
        width: 100px;
        height: 100px;
      }

      to {
        width: 300px;
        height: 300px;
      }
    }

    div {
      width: 100px;
      height: 100px;
      background-color: #17f;

      /*
        animation: name duration timing-function delay iteration-count direction fill-mode play-state;
         ● animation-name
         ● animation-duration
         ● animation-timing-function  速度曲线
         ● animation-delay
         ● animation-iteration-count  播放的次数
         ● animation-direction        播放的方向
         ● animation-fill-mode        在动画开始之前、动画结束之后，元素应用的样式
         ● animation-play-state       播放的状态
       */
      animation: size-animation 1s linear 0s infinite alternate none running;
    }
  </style>
</head>

<body>
  <div></div>
</body>

</html>